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Drywall Calculator

Walls + ceiling coverageOpening deductions includedWaste factor & cost estimate
Enter Room DimensionsFree · Instant
Length (ft)
Width (ft)
Height (ft)
Doors
Windows
Results
466 sq ft
Net Area
before waste
513 sq ft
Area + Waste
+10%
17
Sheets Needed
32 sq ft ea.
Room Breakdown
RoomWallsCeilingNet
Room 1396120466
Total466

How Drywall Quantity Is Calculated

Wall Area = 2 × (Length + Width) × Height
Ceiling Area = Length × Width
Net Area = Wall Area + Ceiling Area − Openings
Sheets = ceil(Net Area × (1 + Waste%) ÷ Sheet Size)

Standard door openings are estimated at 20 sq ft and windows at 15 sq ft. The waste factor accounts for cuts and defects. 10% is typical for simple rooms.

Who Is This Calculator For?

🏠
Homeowners
Plan your renovation and know exactly how many sheets to buy.
🔨
DIY Drywallers
Get accurate sheet counts before your first trip to the hardware store.
🏗️
Contractors
Estimate material costs quickly for new builds or remodels.
💰
Budget Planners
Enter price per sheet to calculate total material cost.

How to Use This Calculator

1
Enter room length and width
Measure the floor dimensions in feet. These are used to calculate wall perimeter and ceiling area.
2
Enter ceiling height
Standard ceiling height is 8 or 9 feet. Enter your actual height.
3
Enter doors and windows
Count standard doors (1) and windows (2 per room average) for opening deductions.
4
Add more rooms
Click 'Add Room' to include multiple rooms in the same estimate.
5
Choose sheet size and waste factor
4×8 sheets (32 sq ft) are most common. Use 10% waste for simple rooms.
6
Enter price per sheet (optional)
If you know current sheet pricing, get an instant total cost estimate.

Worked Example

Tom is drywalling a 12×10 ft bedroom with 9 ft ceilings, 1 door, and 2 windows.

Wall area: 2 × (12+10) × 9 = 396 sq ft
Ceiling area: 12 × 10 = 120 sq ft
Openings: 1 door (20) + 2 windows (30) = 50 sq ft
Net area: 396 + 120 − 50 = 466 sq ft
+10% waste: 466 × 1.1 = 512.6 sq ft
Sheets needed: ceil(512.6 / 32) = 17 sheets

Common Drywall Mistakes to Avoid

!
Skipping the waste factor
Always add at least 10%. Cuts and mistakes are inevitable: buying short means a second store trip mid-project.
!
Using nominal ceiling height
If your ceiling has a drop or soffit, measure actual height, not standard 8 or 9 ft.
!
Forgetting closets and alcoves
Closet walls, built-in niches, and alcoves all need drywall. Add them as separate rooms.
!
Using 1/2" for all surfaces
Ceilings and firewall applications typically require 5/8" Type X. Check local code requirements.
!
Not deducting large openings
Doorways, windows, and built-in areas should be subtracted from your total area estimate.

Frequently Asked Questions

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Sources & References

Drywall Design and Construction Guide
USG Corporation · usg.com
Using Gypsum Board for Walls and Ceilings
Gypsum Association · gypsum.org
International Residential Code: Wall and Ceiling Finish Requirements
IRC · iccsafe.org
Written By
Chris Hendricks
Licensed general contractor, 20+ years residential construction

Chris has managed hundreds of residential remodel and new construction projects across the Pacific Northwest. He specializes in finishing work and interior buildouts.

Thickness Guide
1/4" (Overlay / repairs)
3/8" (Curved walls)
1/2" (Standard walls)
5/8" (Ceilings / fire)
💡 Pro Tip

Run drywall horizontally on walls (long edge across studs). This reduces the number of vertical butt joints, which are harder to finish smoothly than tapered edges. Horizontal orientation also increases wall strength.

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